Conventional rotor balancing methods were tedious and labor intensive. These methods comprised mounting the rotor on a balance machine, turning the rotor to find the imbalance locations, dismounting the rotor, grinding or drilling excess material away from the rotor and remounting the rotor to determine its balance. Since it was difficult to determine the amount of material removed, the whole operation had to be repeated many times and was frequently based on trial-and-error.
In commonly assigned U.S. Pat. No. 4,773,019, a microprocessor controlled laser system is disclosed in which a rotor is mounted on supports with vibration sensors. The sensors are coupled to the microprocessor for using a plurality of influence coefficients descriptive of the vibration changes caused when an amount of material is removed from a particular location on the rotor. A series of laser pulses are issued to remove material from the rotor as calculated by the microprocessor. However, in certain applications, removal of material from a rotor might not be feasible or advisable because, for example, it may weaken the rotor structurally.